21 July 2011

Praying mantis (Mantodea)

Here is a close-up of a praying mantis (Mantodea) from our garden.  They are fascinating insects.  "The articulation of the head is remarkably flexible, permitting nearly 300 degrees of movement in some species, allowing for a great range of vision (their compound eyes have a large binocular field of vision) without having to move the remainder of the body.

They are also masters of disguise, "generally, mantises are protected simply by virtue of concealment. When directly threatened, many mantis species stand tall and spread their forelegs, with their wings fanning out wide. The fanning of the wings evidently makes the mantis seem larger and more threatening, with some species having bright colors and patterns on their hind wings and inner surfaces of their front legs for this purpose. If harassment persists, a mantis may then strike with its forelegs and attempt to pinch or bite. As part of the threat display, some species also may produce a hissing sound by expelling air from the abdominal spiracles.  When flying at night, at least some mantises are able to detect the echolocation sounds produced by bats, and when the frequency begins to increase rapidly, indicating an approaching bat, they will stop flying horizontally and begin a descending spiral toward the safety of the ground, often preceded by an aerial loop or spin.

Mantises,  like stick insects, show rocking behaviour in which the insect makes rhythmic, repetitive side-to-side movements. Functions proposed for this behaviour include the enhancement of crypsis by means of the resemblance to vegetation moving in the wind. However, the repetitive swaying movements may be most important in allowing the insects to discriminate objects from the background by their relative movement, a visual mechanism typical of simpler animals. Rocking movements by these generally sedentary insects may replace flying or running as a source of relative motion of objects in the visual field.

Mantises are camouflaged, and most species make use of protective coloration to blend in with the foliage  or substrate, both to avoid predators themselves, and to better snare their victims. Various species have evolved to not only blend with the foliage, but to mimic it, appearing as either living or withered leaves, sticks, tree bark, blades of grass, flowers, or even stones. Some species in Africa and Australia are able to turn black after a molt following a fire in the region to blend in with the fire ravaged landscape (a type of adaptive melanism referred to as fire melanism). While mantises can bite, they have no venom.  They can also slash captors with their raptorial legs (which is often preceded by a threat display wherein the mantis will rear back and spread its front legs and wings (if present), often revealing vivid colors and/or eyespots to startle a predator). They do not appear to be chemically protected; nearly any large predatory animal will eat a mantis such as Scops owls, shrikes, bullfrogs, chameleons and milk snakes."
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